linux-kernel - Re: REGRESSION: Performance regressions from switching anon

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Message-ID: <BANLkTimStT22tA2YkeuYBzarnnWTnMjiKQ@mail.gmail.com>
Date:	Fri, 17 Jun 2011 11:39:04 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Shaohua Li <shaohua.li@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Russell King <rmk@....linux.org.uk>,
	Paul Mundt <lethal@...ux-sh.org>,
	Jeff Dike <jdike@...toit.com>,
	Richard Weinberger <richard@....at>,
	"Luck, Tony" <tony.luck@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...nel.dk>,
	Namhyung Kim <namhyung@...il.com>,
	"Shi, Alex" <alex.shi@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: REGRESSION: Performance regressions from switching anon_vma->lock
 to mutex

On Fri, Jun 17, 2011 at 11:32 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>
> something like so I guess, completely untested etc..

Having gone over it a bit more, I actually think I prefer to just
special-case the allocation instead.

We already have to drop the anon_vma lock for the "out of memory"
case, and a slight re-organization of clone_anon_vma() makes it easy
to just first try a NOIO allocation with the lock still held, and then
if that fails do the "drop lock, retry, and hard-fail" case.

IOW, something like the attached (on top of the patches already posted
except for your memory reclaim thing)

Hugh, does this fix the lockdep issue?

                        Linus

View attachment "patch.diff" of type "text/x-patch" (2009 bytes)